Testosterone produced by Leydig cells within the testis, in response to stimulation by Luteinizing Hormone secretion by the pituitary gland, is believed to be an important regulator of germ cell development. We propose to explore the hypothesis that abnormalities of testicular androgens or androgen receptors are related to seminiferous tubule dysfunction in some forms of male infertility. Testicular steroid secretion will be studied by repetitive gonadal vein sampling to men with varicocele-related infertility and the findings related to gonadotropin secretion. The androgens present in the seminiferous tubules of human testis will be studied by radioimmunoassay methods following separation by high performance liquid chromatography. Androgen receptors will be studied in seminiferous tubules from humans and cynomolgus monkeys. Finally, Sertoli cell-enriched cultures derived from the testes of prepubertal subhuman primates will be established and androgen metabolism and receptor binding will be explored. Because idiopathic male infertility is a common disorder with no uniformly effective treatment, these studies are of importance to clinicians and investigators in the fields of physiology, endocrinology, biochemistry, urology, and gynecology.